public class Test1 {


    public static void main1(String[] args) {
        String s = String.format("%d-%d-%d", 2019, 9,14);
        System.out.println(s);
    }


    public static void main(String[] args) {
        String s = "hello";
        String tmp = s.replace('l','L');
        String tmp1 = s.replace("l","L");
        String tmp2 = s.replaceAll("l","L");
        String tmp3 = s.replaceFirst("l","L");
        System.out.println(tmp);
        System.out.println(tmp1);
        System.out.println(tmp2);
        System.out.println(tmp3);
    }
}
